Reporting a crime when there has been none is a chargeable offense in most states. The problem is in proving it. You may be able to prove that male A did not rape female A, but that does not mean that she was not raped by male B. She may well have just mistaken him for male A. And then too there are the cases where she believed with all her heart that she was raped, but there just wasn't enough evidence to prove it. He gets off, but that doesn't mean she's committed a crime.

About the only time I can see a case like this actually getting prosecuted is if she admits she made it all up or if there is undisputable evidence that she consented, like a video of the act. Then I'd have no problem with charging her.